Soybean Nodulation Issues

There have been a lot of phone calls and text messages over the past few weeks about lack of nodulation in soybean. Most likely, there are more issues this year with high soybean acres, many of which have historically been cotton and corn ground that was planted to soybean due to market forecasts. Typically, our recommendation is that if a field has not been in soybean in the past 3-5 seasons, it is usually wise to run an inoculant seed treatment. Even then, nodulation isn’t always guaranteed. We have to remember we are introducing a live organism to the environment. So, conditions matter. Time from inoculation until planting, seed treatment combinations, storage temperatures and environments, product age, and soil environments all play a role in viability for those rhizobacteria.

If you have inoculated seed, it is wise to scout those soybeans around the V3 to V4 growth stages looking for nodulation. It is during that time that the nodules should begin to form on the roots. By reproductive phases, the plant begins to primarily depend on those nodules for N uptake. If by late vegetative stages no nodules have formed, we typically recommend applying 60-70 units of N at that point and a second application of 60-70 units of N at the R1 to R2 stage OR 2 to 3 weeks after the first application. The goal should be to identify the issue and apply corrective measures before the crop begins yellowing from N deficiencies.